Lamp



S. STAHL Nav, 23, 1937.

LAMP

Filed Feb. 18, 1935 2 Sheets-Sheet 1 NOV. 23, 1937. I sv STAHL 2,099,830

LAMP

Filed Feb. 18, 1935 2 Sheets-Sheet 2 9B l: E v

no 5a www huyen/MJT ,5 cmLLLQL Shah/L Orlxys Patented Nov. 23, 1937UNITED sTATEs` PATENT OFFICE '1 Claims.

My invention relates to electric lamps, and includes among its objectsand advantages a simplicati'on in lamps which operate by maintaining oneor more arcs inside a transparent bulb.

5 In the accompanying drawings:

Figure 1 is a. side elevation of a lamp according to the invention; A

Figure 2 is a developed section as on the arcuate line 2-2 of Figure 3;

l Figure 3 is a section on line.3-3"cfy Figure. 1;

Figure 4 is a developed section, as in Figure 2,

indicating an alternative arrangement for the f the ionization until anarc is established at 24. Figure 5 is a fragmentary side elevation ofan' starting resistances;

alternative arrangement for vstarting 'the first arc; and

Figure 6 Ais a developedsection, as in Figure 2, indicating anotherarrangement for the `starting resistances.

In the embodiment of the invention selected for illustration, the lampcomprises the usual glass bulb I0 with a threaded socket I2. The standI4 includes three tubes, I6, I8, and 20, extending in parallelism alongthe neck of the bulb and then diverging to support the glass annulus 22at three equally spaced points.

The arcing zone is below the annulus, and in it I position electrodesfor maintaining five arcs at 24, 26, 28, 30, and 32. To deliver currentto these arcs, the button 34 connects with along resistance 36 housed inthe tube I8. The resistance 36 delivers current to the pillar 38carrying the eleci trode 40 at its lower end. A series of similarpillars 42 support bridges 44, 46, 48, and 50,

carrying at their ends the electrodes for the arcs, and the lastelectrode 52 is mounted directly on the pillar 54 which communicateswith the return resistance 56, which is a duplicate of resistance 36 andis housed in the tube I6, and

leads to the shell I2.

Shunting the arcs 24,. 26, 28, 30, and 32, I provide resistances 58, 60,62, 64, and 66. A globule of mercury 68 in the bottom of the bulb keepsthe bulb at all times filled with mer- V cury vapor at pressuresdepending on the temperature of the bulb. Thus at ordinary roomtemperatures the pressure oi the mercury vapor in the bulb will beapproximately 1.2 microns,

whereas if the bulb is heated to 350 C. the mercury vapor in the bulbwill have a pressure only slightly less than atmospheric pressure.

The resistances 58, 60, 62, 64, and 66 each have a resistance' manytimes the resistance of the arcs they shunt, when the lamp is heatedthrough and 55 operating normally, and each resistance has a valuesomewhat lower than the preceding one. Good results may be obtained withshunt resistances at least ten times as high as the resistances of thearcs they shunt. The resistances 36vand 56 are relatively very low, andwhen line voltage 5 is first delivered to the lamp, a disproportionateshare cf the available energy is developed in resistance 58. l Theresultant local heating in the vicinity of the arc 24 will heat theadjacent electrodes l0 and the mercury vapor around them, and thewarming up of the lamp as a whole will increase The resulting reducedresistance in the lamp as a Whole will result in material increase incur- `l5 rent which will materially increase the temperatures of theresistances 60, 62, 64, and 66.

The shunting of lament 58 will reduce the resistance in the lamp andwill result in a material increase in current. Now filament 60 will 20become incandescent because it has the highest resistance and heats thegap for the arc 26 and ionizes the mercury7 vapor at this point,establishing ari: 26. Filament 62 now becomes incandescent because nowit is the highest resist- 25 'ance in the circuit, and ionizes .thevapor to establish the arc 28. Then filament 64 will follow the sameprocessand establish arc 30. The filament, 66 will'now becomeincandescent as the others have done and establish the last 30 arc 32.On shunting each arc an increase of current occurs in the circuit. Thearcs may be arranged to open in any order, so far as their geometricallocation is concerned. After all ve arcs are functioning, the relativelylow resist- 35 ances 36 and 56 remain to protect the lamp againstexcessive current ilow. Thus, with arcs designed to operate with afifteen Volt drop and a line voltage of I20, the protecting resistances36 and 56 will need to take care of the remain- 40 ing 45 volts, andtherefore each have a resistance about one and one-half times that of anindividual arc.

The resistances designed to remain permanently in the circuit to protectthe lamp may be 45 positioned anywhere in the circuit of which the lampforms a part. In the case of inside resistances I have indicated onearrangement in Figure 2 which consists of housing them in the tubes I6and I8 of the stand. This afforfisthem 50 an eiective radiating capacitymany /times greater than that of one of the arcs, so that they will notbe heated materially above the temperature of their environment.

Referring now to Figure 4, I have indicated a y single resistance 10spanning both arcs 26 and 28, and a single resistance 'l2 spanning botharcs 38 and 32. In certain types of construction the cost of manufacturereduction in the number of filaments and filament attachments. I havealso indicated protective resistances 14 and I6 arranged to operate attemperatures of incandescence. This is advantageous when the uses towhich the lamp is to be put make it desirable to have blended with thelight from the arcs a percentage of light having the diierent spectralcharacteristics of an incandescent metal.

end electrodes to additional pillars 84 and 86. This positions theincandescent laments 8U and 82 where their geometrical location is bestfor effective radiation of the light from them.

Additional desirable constituents in the light from the lamp, as well asmaterially difl'e'rent starting characteristics may be obtained by theuse of an additional lllng of argon or other in- 4ert gases. Because theincandescent illaments close below the arcs they shunt, such a gas llingenables a relatively low degree of incandescence to generate localionization in the gas filling that will assist the establishment of aglow discharge lled by a gas arc, and thus establish the arcs with lessheating. The reduction in the necessary heat supply makes it possible touse higher shunt resistances and thus increase the eiliciency of thelamp for permanent operating conditions. Also, if the lling is desiredfor starting only, a relatively low pressure not only facilitates theestablishment of the arcs, but when the temperature has built up themercury vapor pressure to a substantial volume, the minute mospheresubstantially of mercury only where gli; inert gas is present inrelatively minute quan- Where an inert gas filling is employed, the rstarc may advantageously be arranged as in Figure 5 where the electrodes88 and 88 are connected with the electrodes 48 and the bridge 44respectively by resistances 82 and 84. The short gap between theelectrodes 88 and 80 causes the immediate establishment of a glowdischarge filled by an arc at this point, and the radiation. from thesmall arc rapidly ionizes the space to be oc, cupied by the long arc 24enough to cause the establishment of the arc 24. 'I'he glow dischargeand establishment o1' the arc may be facilitated sistances 92 and 94need be only slightly contaminated to accomplish a large increase inionization. Afterr the arc 24 isL established, the intensity of the arcbetween the electrodes 88 and 98 will be so reduced by reason o1' theresistances 92 i is materially reduced by the 60, 62, 64, and 66 withthe maximum values that can be used and still generate enough heat tostart the lamp, the arcs 24, 26, 28, and 30, even after establishment,will burn with relatively low intensity until the arc 32 starts, and atthat time the entire lamp will blaze up with full strength. Such a lampwill be relatively slow to start, but after it is functioning, the highresistances employed in shunt will reduce to a negligible percentage theenergy dissipated in those resistances.

For a lamp that is to be turned on and oi repeatedly at short intervalsand that needs to go into operation much more quickly, the use of lowerresistance values, particularly for resistances 60, 62, 64, and 66, willenable the arcs already established to burn much more vigorously. Withsuch an arrangement the arcs can be established much more quickly, andthe lamp will heat up much more promptly to a suitable operatingcondition.

It should also be noted that partial failure of 58 to 66, inclusive, asfor in manufacture, will not render the lamp inoperative unless ,thefailure is complete. Thus, if resistance 64 happened to have amechanical defect that made its actual resistance much higher than thatintended, arc 30 might get started before, arcs 28 and 26, but the lampwould still start, and after it was started, the mechanical defect wouldhave no effect other than a slight increase in eiliciency with respectto the arc 30.

The use for starting purposes of a heat source other than the arc itselfmakes it possible to design and proportion the arcs for operatingconditions, substantially without regard to starting conditions.

Without further elaboration, the foregoing will so fully explain myinvention that others may, by applying knowledge current the time ofapplication, readily adapt the same for use under various conditions ofservice. For instance, when particular portions of the spectrum aredesired for use, the bulb should be of a material transparent to thosewave lengths.

I claim:

l. In a metal vapor arc lamp, a bulb, a metal lling in said bulb,stationary terminals in said bulb for maintaining a plurality of arcsarranged in series,`and shunt heating resistances for eachy arc, one ofsaid heating resistances being of higher resistance than any of therest.

3. In a metal vapor arc lamp, a bulb, a metal lling in said bulb,stationary terminals in said being of higher resistance than any of therest.

4. In a metal vapor arc lamp, a bulb, a metal decreasing resistancevalues, whereby said arcs are established in a predeterminedsequenceinthe order of said resistance values, an arc adjacent the shuntof highest resistance being established rst, the arc with the highestresistance being at one end and each adjacent arc throughout the serieshaving a lower shunt resistance than the preceding one.

5. In a vapor arc lamp, a bulb, electrodes in said bulb for setting up aplurality of peripheral arcs substantially all in the same planeencircling the center of the bulb and spaced outwardly from said centertoward the periphery of the bulb, and lead wires for delivering currentto said electrodes.

6. In a vapor arc lamp, a bulb having substantially the shape of asurface of revolution, and

said arcs and positioned to heat and ionize the lo spaces occupied byall of them, said resistance being electrically connected to the remoteend terminals only of the arcs at opposite ends of the series.

SAMUEL STAHL.

